1. Field of the Invention
The present invention relates to a polymer resin composition and a method of manufacturing the same, and more particularly, to an inexpensive polymer resin composition that provides a uniform color even at resin flow lines or resin weld lines in a molded product manufactured therefrom and which does not deteriorate physical properties of the polymer resin therein, and a method of preparing the same.
2. Description of the Related Art
As customer requirements diversify along with industrial development, the need for polymer resin molded products having an elegant appearance and a high-quality texture increases.
In particular, the appearances of polymer resin molded products have been diversified using special effects providing, for example, metallic textures, pearl textures, holographic textures, marble textures, etc.
Referring to FIG. 1, a method of providing a metallic texture or a pearl texture includes preparing a polymer resin composition that includes a flaky pigment 2 providing such a textual effect and then directly molding the polymer resin composition into a product having a metallic or pearl textured appearance.
Polymeric molded products formed using this method have luminescent properties due to the flaky pigment reflecting light 4. To provide luminosity to such a polymeric molded product, flaky pigment particles 2 that maximize the reflection of light 4 and do not greatly affect the volume or physical properties of a polymer resin are used. This method is cheaper than a conventional spray coating method and does not cause environmental problems associated with conventional spray coating methods.
However, when molding a product using the above-described method using flaky pigment particles 2, the orientation of the flaky pigment particles 2 changes in a resin flow line or a resin weld line 1 in which polymer resin flows intersect or weld, from a direction parallel to a surface of the product to a direction perpendicular to the surface of the product (refer to FIG. 1). As a result, the reflection of light 5 in the resin flow line or resin weld line 1 decreases, thereby resulting in a dark line on the surface of the product degrading the product's appearance.
To eliminate such an appearance-degrading factor, the amount of flaky pigment particles can be reduced. However, reducing the amount of flaky pigment particles results in an attenuate texture. In addition, there has been a suggestion to increase the size of the flaky pigment particles. However, the use of increased flaky pigment particles results in a rough and inferior product appearance.
To solve these problems, as shown in FIG. 2, a method of using polyhedral pigment particles 3 instead of flaky pigment particles has been suggested. The use of polyhedral pigment particles 3 is effective to some extent because polyhedral pigment particles 3 do not greatly affect the reflection of light 4, 6 irrespective of their orientation. However, a much larger amount of polyhedral pigment particles relative to the amount of flaky pigment particles is required to obtain a similar luminosity obtained by flaky pigment particles. Therefore, this method increases the product cost, results in degradation in physical properties such as elongation, impact strength, etc., due to the use of a relatively smaller amount of polymer resin, and increases the weight of the product.
To overcome these problems, experiments have been conducted to increase the luminosity with a smaller amount of polyhedral pigment particles (Japanese Laid-open Nos. 8-109340; 9-194630; and 10-265676). However, there is a substantial limit to increase the luminosity only using polyhedral pigment particles, and thus an improvement is required.
As a result of research continuously performed to solve the above-described problems, the inventors of the present invention have found a method of selectively distributing flaky pigment particles and polyhedral pigment particles in a composition so as not to degrade the appearance of a product manufactured therefrom even in a resin flow line and a resin weld line.